POPULATION TREND: Old-growth forests in the range of the California spotted owl have declined by roughly 90 percent, with an indeterminable but likely severe impact on the owl. Studies from the 1990s showed annual declines in California spotted owl populations of five to 10 percent. A recent reanalysis of population data by the U.S. Forest Service found similar declines, but because of a lack of statistical certainty, concluded that the rate of decline was uncertain.